Method for control of an internal combustion engine with a variable valve control

ABSTRACT

The invention relates to a process for controlling an internal combustion engine, whereby the internal combustion engine is equipped with a device to change a valve timing. To permit a change in the valve timing only when it is necessary for the operation of the internal combustion engine, it is proposed that a transmission, connected at the end of the internal combustion engine, be monitored as to whether a shift operation is taking place in the transmission. If such a shift operation is recognized, a change in the valve timing is suppressed.

[0001] The invention relates to a process for the control of an internal combustion engine, whereby the internal combustion engine is equipped with a device to change a valve timing. A change in the valve timing means in this connection that variables of the valve timing, such as valve lift or phase position, can be adjusted by means of well-known means.

[0002] In such devices a change in the valve timing takes place as a function of the different operating parameters of the internal combustion engine. Such an operating parameter can be, for example, the actual load of the internal combustion engine. One possibility of detecting such a load is to scan the position of a throttle flap of the internal combustion engine. In particular in devices to change the valve timing, in which the valve timing is not adjusted continuously, but in steps, a change in the load of the internal combustion engine results in a change in the valve timing, when a load threshold, determined for the change over between steps, is exceeded. If the load of the internal combustion engine changes often in the area of the load threshold, the result is frequent shift operations in the valve timing, and thus an increased wear and under some circumstances also an unsatisfactory operating performance of the internal combustion engine.

[0003] Proceeding from this state of the art, the object of the invention is to provide a process to control an internal combustion engine with variable valve timing, in which a change in the valve timing takes place only when it is necessary for the operation of the internal combustion engine.

[0004] The invention solves this problem with the features of patent claim 1. The invention is based on the knowledge that a change in the load of the internal combustion engine takes place especially when there is a shift operation in the transmission, connected at the end of the internal combustion engine. Therefore, it is proposed that the transmission, connected at the end of the internal combustion engine, be monitored as to whether there is a shift operation in the transmission. If such a shift operation is recognized, a change in the valve timing is suppressed. With this process the number of changes in the valve timing is significantly reduced in an advantageous manner and thus the wear properties of the valve timing and optionally the operating behavior of the internal combustion engine are improved, since now it is prevented that during a shift operation in the transmission the performance characteristics of the internal combustion engine are additionally affected by a change in the valve timing.

[0005] Advantageous further developments of the invention are described in the dependent claims.

[0006] Thus, to recognize a shift operation in a manual transmission, it is proposed that a clutch be monitored and in the case of an open clutch to conclude a shift operation. Such a monitoring can be performed, for example, in a very simple manner by scanning a clutch switch on the clutch pedal. Precisely in the case of a manual transmission the change in the load of the internal combustion engine is especially high, because here for a shift operation the load of the internal combustion engine is reduced to zero. In the case of an automatic transmission a shift operation can be recognized because a controller of the automatic transmission sends a signal, when this controller triggers a shift operation. Such a signal can be especially easy to generate and passed on, when the controller of the automatic transmission is connected to a controller for the valve timing by way of a databus, for example a CAN bus.

[0007] A shift operation can be recognized totally independently of the design of the transmission, in that a wheel speed signal is put in relation to a motor speed signal. Should this relation change, then a shift operation has taken place, or the force flow between the internal combustion engine and the wheels of the motor vehicle has been interrupted in a different manner. This process can be implemented in a very simple manner, because the wheel speed signals are already detected in all motor vehicles as the driving speed signal or for an antilock braking system.

[0008] Finally it can be provided that after a recognized shift operation a change in the valve timing be suppressed for a predetermined period of time (i.e. a dead time), which follows immediately, in order to prevent in this manner that a load adjustment after a shift operation result in a change in the valve timing.

[0009] The invention is described in detail below with reference to the embodiment depicted in the figures.

[0010]FIG. 1 is a drawing of a drive train of a motor vehicle, with a manual transmission.

[0011]FIG. 2 is a detail of the drawing, according to FIG. 1, but for an automatic transmission.

[0012]FIG. 3 is a flow diagram of an inventive process to control an internal combustion engine.

[0013]FIG. 4 depicts a process to recognize a shift operation for the process, according to FIG. 3, and

[0014]FIG. 5 depicts an alternative process to recognize a shift operation for the process, according to FIG. 3.

[0015] The drive train, depicted in FIG. 1, for a motor vehicle comprises an internal combustion engine 1, a manual transmission 2, which is connected at the end of the internal combustion engine 1, a cardan shaft 3 to connect the transmission 2 to a differential 4, and two articulated shafts 5, which connect the differential 4 to the driven wheels 6. The two other wheels 7 are not driven. A controller 8 receives as the operating variables from the internal combustion engine 1 a signal DK for the throttle flap position and thus for the load of the internal combustion engine 1. In addition, the controller 8 receives from the internal combustion engine 1 a signal n_(mot) for the speed of the internal combustion engine 1.

[0016] The internal combustion engine 1 is equipped with a variable valve timing, as disclosed in detail, for example, in the DE 40 06 910 A1 (=U.S. Pat. No. 5,120,278). The controller 8 controls this device to change the valve timing by way of a signal uv in such a manner that at the value of the signal uv=0 a first phase position in the valve timing is set and at a signal uv=1 a second phase position in the valve timing is set.

[0017] Finally the controller 8 receives a signal of a driving speed v of the motor vehicle from a signal generator 9 and the signal k of a clutch switch 10, which monitors the position of a clutch pedal 11. The clutch pedal 11 actuates a clutch 12, disposed in the transmission 2.

[0018] The arrangement of the signal generator 9 at the differential 4 has the effect that the signal v for the driving speed is determined as the mean value of the wheel speeds of the driven wheels 6.

[0019]FIG. 2 is a detail of the drawing, according to FIG. 1, of a drive train with an automatic transmission 13. An automatic transmission means in this connection that the force flow in the transmission 13 is not interrupted by the driver and a clutch pedal 11, but rather by means of a controller 14 of the automatic transmission 13. The rest of the construction of the automatic transmission 13 is immaterial.

[0020] The signal connections between the controller 8 and the internal combustion engine 1 are unchanged with respect to FIG. 1. The signal k from the clutch switch 10 is replaced here by a signal k for a shift operation, which is exchanged by way of a CAN databus between the controller 8 and the control 14 of the automatic transmission 13. The rest of the drive train is unchanged with respect to FIG. 1.

[0021]FIG. 3 is a flow chart of a (sub) routine in the controller 8. In a first step 20 the transmission 2 or the automatic transmission 13 is monitored as to whether a shift operation is taking place in the transmission. If such a shift operation is recognized, the program continues with the next step 21, in that a change in the signal uv is suppressed for the duration of the shift operation. Immediately following step 21, a change in the signal uv is further suppressed for an additional period of time tz in a step 22. This period of time tz is dimensioned in such a manner that changes in the signal DK and thus the load of the internal combustion engine 1, which is connected to the shift operation in the transmission 2, 13 that has just finished, occur in this period of time tz. When this period of time tz has expired, or if no shift operation was recognized in step 20, the program is finished, and the controller 8 passes over to other parts of the program, which are not illustrated here.

[0022]FIG. 4 shows a first possibility to recognize a shift operation in step 20. To this end, it is tested whether the signal k assumes the value 1. If this is the case, then the program branches off to step 21. Otherwise, the program is terminated, according to FIG. 3. The signal k assumes the value 1 in the following cases:

[0023] In the case of a manual transmission 2, according to FIG. 1, when the clutch pedal 11 is moved out of its idle position and thus a separation of the clutch 12 is introduced; or

[0024] In the case of an automatic transmission 13, according to FIG. 2, as long as the control 14 performs a shift operation in the transmission 13.

[0025]FIG. 5 shows an alternative process for recognizing a shift operation in step 20. First, in a step 23 the signals n_(mot) for a speed of the internal combustion engine 1 and v for a driving speed are detected. In a subsequent step 24 a relation i(t) of the signals n_(mot) and v is formed. In a step 25 a deviation di of the actual relation i(t) to a predetermined relation i(t−1) is calculated. In a subsequent step 26 the actual relation i(t) is stored as the preceding relation i(t−1). In a step 27 it is tested whether the amount of the deviation is above a maximum value d_(max). If this is the case, then a shift operation is recognized and the program branches off to step 21. Otherwise, the program ends in accordance with FIG. 3.

[0026] The maximum value d_(max) for the amount of deviation di indicates a reliable deviation that does not yet point to a shift operation or any other operation, having an additional effect on the load of the internal combustion engine 1. In the case of a manual transmission 2 the maximum value d_(max) can assume a value of essentially zero. In an automatic transmission 13 it must be taken into consideration as a function of the model that a change in the relation i(t) can be induced even outside a shift operation. For example, this can be the case when the automatic transmission 13 is provided with a hydraulic torque converter on the input side. By selecting the size of the maximum value d_(max) it can be determined in this case whether, for example, a slip in the said torque converter to suppress the change in the valve timing should or should not take place. 

Patent claims
 1. Process for the control of an internal combustion engine, whereby the internal combustion engine (1) is equipped with a device (8) to change a valve timing, characterized by the following steps: monitor a transmission (2, 13), which is connected at the end of the internal combustion engine, as to whether a shift operation is taking place in the transmission, suppress a change in the valve timing, when a shift operation is recognized.
 2. Process, as claimed in claim 1, characterized in that to recognize a shift operation in the case of a manual transmission (2) a clutch (12) is monitored, and in the case of an open clutch the conclusion is a shift operation.
 3. Process, as claimed in claim 1, characterized in that to recognize a shift operation in the case of an automatic transmission (13) a signal (k) is sent from a controller (14) of the automatic transmission, when the controller triggers a shift operation.
 4. Process, as claimed in claim 1, characterized in that to recognize a shift operation a wheel speed signal (v) is put in relation (di) to a motor speed signal (nmot), and if there is a change in the relation, a shift operation is inferred.
 5. Process, as claimed in any one of the preceding claims, characterized in that after a recognized shift operation a change in the valve timing is further suppressed for a predetermined period of time (tz), which follows immediately. 